Each of these macro constants expands to a nonnegative integer constant expression, which can be used with fesetround and fegetround to indicate one of the supported floating-point rounding modes. The implementation may define additional rounding mode constants in <fenv.h>, which should all begin with FE_ followed by at least one uppercase letter. Each macro is only defined if it is supported.

On most implementations, these macro constants expand to the values equal to the values of FLT_ROUNDS and float_round_style